The patch titled
Subject: Compiler Attributes: check GCC version for __alloc_size attribute
has been added to the -mm tree. Its filename is
compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix.patch
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------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: Compiler Attributes: check GCC version for __alloc_size attribute
Unfortunately, just version checking the use of
-Wno-alloc-size-larger-than is not sufficient to make the __alloc_size
attribute behave correctly under older GCC versions. The attribute itself
must be disabled in those situations too, as there appears to be no way to
reliably silence the SIZE_MAX constant expression cases for GCC versions
less than 9.1:
In file included from ./include/linux/resource_ext.h:11,
from ./include/linux/pci.h:40,
from drivers/net/ethernet/intel/ixgbe/ixgbe.h:9,
from drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c:4:
In function 'kmalloc_node',
inlined from 'ixgbe_alloc_q_vector' at ./include/linux/slab.h:743:9:
./include/linux/slab.h:618:9: error: argument 1 value '18446744073709551615' exceeds maximum object size 9223372036854775807 [-Werror=alloc-size-larger-than=]
return __kmalloc_node(size, flags, node);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/slab.h: In function 'ixgbe_alloc_q_vector':
./include/linux/slab.h:455:7: note: in a call to allocation function '__kmalloc_node' declared here
void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_slab_alignment __malloc;
^~~~~~~~~~~~~~
Specifically:
-Wno-alloc-size-larger-than is not correctly handled by GCC < 9.1
https://godbolt.org/z/hqsfG7q84 (doesn't disable)
https://godbolt.org/z/P9jdrPTYh (doesn't admit to not knowing about option)
https://godbolt.org/z/465TPMWKb (only warns when other warnings appear)
-Walloc-size-larger-than=18446744073709551615 is not handled by GCC < 8.2
https://godbolt.org/z/73hh1EPxz (ignores numeric value)
Link: https://lkml.kernel.org/r/20210910201132.3809437-1-keescook@xxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Miguel Ojeda <ojeda@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Arvind Sankar <nivedita@xxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/compiler-gcc.h | 9 +++++++++
include/linux/compiler_attributes.h | 6 ------
include/linux/compiler_types.h | 5 +++++
3 files changed, 14 insertions(+), 6 deletions(-)
--- a/include/linux/compiler_attributes.h~compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix
+++ a/include/linux/compiler_attributes.h
@@ -54,12 +54,6 @@
#define __aligned_largest __attribute__((__aligned__))
/*
- * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
- * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
- */
-#define __alloc_size(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
-
-/*
* Note: users of __always_inline currently do not write "inline" themselves,
* which seems to be required by gcc to apply the attribute according
* to its docs (and also "warning: always_inline function might not be
--- a/include/linux/compiler-gcc.h~compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix
+++ a/include/linux/compiler-gcc.h
@@ -153,3 +153,12 @@
#else
#define __diag_GCC_8(s)
#endif
+
+/*
+ * https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
+ * However, prior to 9.1, -Wno-alloc-size-larger-than does not work,
+ * making this attribute unusable.
+ */
+#if GCC_VERSION < 90100
+#define __alloc_size(x, ...) /**/
+#endif
--- a/include/linux/compiler_types.h~compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix
+++ a/include/linux/compiler_types.h
@@ -254,6 +254,11 @@ struct ftrace_likely_data {
#define asm_volatile_goto(x...) asm goto(x)
#endif
+/* If not specifically disabled, allow the use of __alloc_size attribute. */
+#ifndef __alloc_size
+# define __alloc_size(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
+#endif
+
#ifdef CONFIG_CC_HAS_ASM_INLINE
#define asm_inline asm __inline
#else
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
rapidio-avoid-bogus-__alloc_size-warning.patch
compiler-attributes-add-__alloc_size-for-better-bounds-checking.patch
compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix.patch
checkpatch-add-__alloc_size-to-known-attribute.patch
slab-clean-up-function-declarations.patch
slab-add-__alloc_size-attributes-for-better-bounds-checking.patch
mm-page_alloc-add-__alloc_size-attributes-for-better-bounds-checking.patch
percpu-add-__alloc_size-attributes-for-better-bounds-checking.patch
mm-vmalloc-add-__alloc_size-attributes-for-better-bounds-checking.patch
